Scott,
I think the cooling system pulls from the bottom of the radiator, through the engine, through the thermostat and into the top tank. If this is indeed how the systems functions, I would expect the radiator to be warmer on top and less warm on the bottom...how much of a difference I don't know.
Usually any blockage in the radiator results in OVERHEATING. You are saying yours is not reaching the proper temp...I don't know if this line of reasoning changes when you get into an area of 20 below...brrrrrrrrr!
Stuart
